Terms used in storage projects

The formal act by which an operator takes over a completed system as meeting the contract. Acceptance starts the warranty period running and triggers the final payment. Acceptance can happen subject to reservation, where minor defects are recorded and fixed within a deadline.

The full set of checks carried out before and during acceptance: document review, visual inspection, safety inspection, function tests and the capacity test. It confirms that the built system matches the contractually committed properties before the warranty begins.

The Bundesnetzagentur’s name for its ongoing determination proceeding on the general electricity grid-fee system. Among other things, the proceeding is meant to bring storage systems and generation plants into grid-cost sharing going forward. An interim position of 27 May 2026 confirms the existing exemption under §118(6) EnWG for systems already running; a final determination was still pending at the time of publication.

A plot of every quarter-hour value in a year, sorted by size from largest to smallest rather than by time. It shows how often a given load level is reached or exceeded, and is a central basis for storage sizing.

The highest average power value measured at a connection point within a year. Under §17(2) StromNEV, this single value determines the capacity-charge share of grid fees for the billing year in which it occurs.

A connection situation where a customer’s annual peak load foreseeably and materially differs from the simultaneous annual peak load of all grid users. Under §19(2) StromNEV, an individual, reduced grid fee can be agreed for this.

The floor value of a load profile, below which a connection point’s consumption practically never falls. A high base load relative to peak load points to a steadily operating business without pronounced load peaks.

The control unit of a battery storage system that monitors cell voltages, temperature and state of charge, and keeps charge and discharge within safe limits. The battery management system’s log files are part of the documentation at commissioning and acceptance.

The detailed breakdown of every service and item required under a tender, from which a bidder calculates its quote. It supplements the specification with the concrete structure by trade and item.

A system’s ability to start up on its own without external grid voltage. It is often assumed silently, even though it requires additional hardware that must be explicitly required in the specification.

The ratio of a storage system’s charge or discharge power to its usable capacity, expressed as a multiple per hour. A C-rate of 0.5 means the system can be fully charged or discharged in two hours.

The grid-fee component calculated from a connection point’s annual peak demand multiplied by the annual capacity price per kilowatt the grid operator publishes. Unlike the energy charge, it is set by the single worst moment of the billing year, whatever the average consumption.

Measuring a storage system’s actually usable capacity under controlled conditions as part of acceptance. The result is compared with the contractually committed value; a deviation outside the agreed tolerance counts as a defect.

Representing the operator’s interests during planning, construction and acceptance of a system, independent of the installer. English usage in the German market also calls this owner’s engineering.

The technical process by which a system is put into operation for the first time and tested for function. Commissioning is distinct from formal acceptance, which marks the start of the warranty and can happen at a later date.

The Bundesnetzagentur’s central official register in which electricity and gas installations, including storage systems, must be registered. Registration is required regardless of any grid-fee exemption.

The number of charge and discharge cycles a battery can go through at a defined depth of discharge before its capacity falls below an agreed limit. It is a central figure for warranty terms and quote comparison.

The share of a storage system’s usable capacity actually drawn on during a discharge, given in percent. A high depth of discharge over many cycles usually speeds up cell ageing.

The European standard that sets requirements, a common methodology and result formats for energy audits. It applies to businesses and organisations of every kind and every energy form, with the exception of individual private residential buildings, and forms the methodological basis for energy audits under the EDL-G.

The Energy Services Act (Energiedienstleistungsgesetz). It obliges non-SMEs below the EnEfG management threshold to run an energy audit every four years, and remains in force alongside the EnEfG.

Supplying selected loads with electricity if the public grid fails, usually after a brief switchover time. Emergency-power capability must be explicitly stated as a requirement in the specification, since it needs additional hardware.

The Energy Efficiency Act (Energieeffizienzgesetz), in force since 18 November 2023. It obliges companies above an average annual energy consumption of 7.5 GWh to run an energy or environmental management system, and above 2.5 GWh to publish implementation plans.

A systematic review of an organisation’s energy consumption following the methodology of DIN EN 16247-1, aimed at identifying savings potential. For non-SMEs below the EnEfG management threshold, it is mandatory every four years under §8 EDL-G.

The grid-fee component charged per kilowatt-hour consumed. The capacity charge, by contrast, is based on the highest measured power of a year.

A systematic, ongoing process to steer and continually improve an organisation’s energy efficiency, usually certified to ISO 50001. It differs from a one-off energy audit through annual surveillance and re-certification every three years.

The technical and regulatory check of whether, and at what scale, a storage system makes sense at a given site. It brings together load-profile analysis, site conditions and regulatory deadlines such as §118(6) EnWG.

The contracting party responsible for the turnkey delivery of a system under a single contract, engaging installation partners and further subcontractors to do so. In this model, the operator has a single point of contact for the entire scope.

The technical and contractual link between a site and the public electricity grid, defined by voltage level and permitted connection power. It determines which technical connection rules, such as VDE-AR-N 4105 or VDE-AR-N 4110, apply to a system.

The fee a grid user pays the grid operator for using the electricity grid, made up of the energy charge, the capacity charge and further components. Certain storage systems are temporarily exempt from part of this fee under §118(6) EnWG.

The company that operates a distribution or transmission grid for electricity and is responsible for grid connection, grid fees and the technical inspection of new systems. It is the central point of contact in any storage project.

A time window defined by the grid operator, in which experience shows a particularly high grid load occurs in its network area. Consumption outside these windows can be a condition for reduced individual grid fees.

The concrete, implementable plan required under §9 EnEfG for carrying out economically viable final-energy-saving measures. It must be published within three years of completing management-system certification or an energy audit.

A specialist firm engaged by the general contractor or installer to carry out part of the construction or installation work on site. ZNX has no own installation team and works through vetted installation partners for turnkey delivery.

The company that actually builds and commissions a system, as distinct from the general contractor, who carries overall project responsibility without necessarily installing anything themselves. A specification should clearly separate the installer’s services from those of other parties.

Operating a system disconnected from the public grid, for instance during a grid outage. Island mode needs additional hardware and control logic. A standard system does not have them unless the specification explicitly requires them.

The international standard for energy management systems. It sets requirements for building, running and continually improving an energy management system, backed by annual surveillance audits and re-certification every three years.

The international standard for carrying out energy audits. It sets principles and requirements similar to those of DIN EN 16247-1, with a stronger focus on methodical data analysis.

The German term for peak shaving, which means using a storage system to reduce load peaks. German documents often pair the two terms as Lastspitzenkappung (Peak Shaving).

A short-term rise in power draw well above the usual level. A single load peak within a year can decide the annual peak demand, and with it the capacity charge for the billing year in which it occurs.

The time series of a connection point’s electricity consumption, recorded in quarter-hour intervals under registering capacity metering. A year contains 35,040 such values, the most complete description a company has of its own consumption.

Another term for registering capacity metering, where consumption is recorded in quarter-hour intervals and sent to the metering point operator. It is the precondition for RLM billing.

The voltage level up to roughly one kilovolt, to which most small and medium connection points are connected. Systems at this level follow the technical connection rules under VDE-AR-N 4105.

The voltage level of roughly one to 36 kilovolts, to which larger connection points and generation plants are connected. Systems at this level follow the technical connection rules under VDE-AR-N 4110.

The company that operates and reads the meters at a connection point and provides the consumption data, including the load profile under registering capacity metering. It can, but need not, be the same company as the grid operator.

Technical client representation that looks after the operator’s interests during planning, construction and acceptance of a system, independent of the installer. The German market uses the English term directly.

The targeted reduction of load peaks by a storage system that supplies power from its own buffer at critical moments instead of drawing from the grid. The German market often writes this as Lastspitzenkappung (Peak Shaving).

The ratio between a load profile’s peak load and its average load. High peakiness points to a few short load peaks against otherwise steady consumption, and tends to favour using a storage system for peak shaving.

A single measured value of a load profile, averaged over a quarter hour. A year consists of 35,040 such values, from which figures including the annual peak demand are derived.

Comparing several storage quotes on a common, normalised basis, such as usable rather than nameplate capacity and continuous rather than peak power. It also uncovers differences in scope, for instance whether grid connection, fire protection or commissioning are included in the quote.

Registering capacity metering. Grid operators currently apply it, as a matter of practice, to connection points with annual consumption above 100,000 kWh; below that threshold a standard load profile is generally used instead. It records consumption in quarter-hour intervals and is the basis of capacity-charge billing.

The ratio of the energy recovered when discharging a storage system to the energy put in when charging it, given in percent. It is one of the central figures that must be normalised to comparable test conditions during a quote review.

The share of self-generated electricity, for instance from a PV system, consumed directly on site rather than fed into the grid. A storage system can raise the self-consumption share by buffering surplus generation.

A customer whose consumption is estimated from a standard load profile rather than measured. Grid operators currently apply this below 100,000 kWh of annual consumption. Switching to RLM metering changes the price structure fundamentally.

The document that fixes the technical and contractual requirements for a system, from performance data through warranty to the later acceptance criteria. It is the basis of every tender and every later quote comparison.

The process by which an operator gathers quotes from several suppliers based on a specification. A clean tender ensures every bidder receives the same requirements, so the quotes that come back are comparable.

A system that switches to stored energy without a noticeable break if the grid fails. UPS function is distinct from a standard storage system and must be stated as a requirement of its own in the specification.

The share of a storage system’s capacity actually available in operation, after deducting reserve and depth-of-discharge limits. It differs from the nameplate capacity of the installed cells and should be explicitly required in every specification.

The calculated number of hours obtained by dividing a connection point’s annual consumption by its annual peak demand. High utilisation hours indicate steady, intensive grid use and are the basis for reduced individual grid fees under §19(2) StromNEV.

The technical application rule for connecting and operating generation and storage systems on the low-voltage grid. It applies regardless of technology and covers, among other things, protective devices and how a system behaves during a grid fault.

The technical application rule for connecting generation and storage systems to the medium-voltage grid. Compared with VDE-AR-N 4105, it adds requirements, for instance on how a system behaves during a brief grid fault.

The statutory basis for the grid-fee exemption of newly built electricity storage systems. Systems commissioned between 4 August 2011 and 4 August 2029 are exempt from grid fees on the energy drawn for storage for 20 years from commissioning, provided the energy drawn is fed back, with a time offset, into the same grid.

The rule under which grid users with atypical or intensive grid use can apply to the grid operator for an individual, reduced grid fee. It relates closely to using a storage system for peak shaving, because that directly changes the figures the rule is based on.